The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing charge enhancing additives, which impart or assist in imparting a positive charge to the toner resin particles and can enable toners with rapid admix characteristics. In one embodiment, there are provided in accordance with the present invention toner compositions comprised of resin particles, pigment particles, and quaternary ammonium hydrogen bisulfates, including distearyl methyl hydrogen ammonium bisulfate. In one embodiment, the present invention is directed to toners with charge additives of tetraalkylammonium sulfonates such as dimethyl distearyl ammonium alkyl or perfluoralkyl sulfonates. The aforementioned additives in embodiments of the present invention enable, for example, toners with rapid admix of less than about 15 seconds, extended developer life, stable electrical properties, high image print quality with substantially no background deposits, and compatibility with fuser rolls including Viton fuser rolls. Also, the aforementioned toner compositions usually contain pigment particles comprised of, for example, carbon black, magnetites, or mixtures thereof, cyan, magenta, yellow, blue, green, red, or brown components, or mixtures thereof thereby providing for the development and generation of black and/or colored images. The toner compositions of the present invention in embodiments thereof possess excellent admix characteristics as indicated herein, and maintain their triboelectric charging characteristics for an extended number of imaging cycles exceeding, for example, 1,000,000 in a number of embodiments. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic, imaging and printing processes, including color processes.
Developer compositions with charge enhancing additives, which impart a positive charge to the toner resin, are known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions. In this patent, there are disclosed quaternary ammonium compounds with four R substituents on the nitrogen atom, which substituents represent an aliphatic hydrocarbon group having 7 or less, and preferably about 3 to about 7 carbon atoms, including straight and branch chain aliphatic hydrocarbon atoms, and wherein X represents an anionic function including, according to this patent, a variety of conventional anionic moieties such as halides, phosphates, acetates, nitrates, benzoates, methylsulfates, perchloride, tetrafluoroborate, benzene sulfonate, and the like. U.S. Pat. No. 4,221,856 which discloses electrophotographic toners containing resin compatible quaternary ammonium compounds in which at least two R radicals are hydrocarbons having from 8 to about 22 carbon atoms, each other R is a hydrogen or hydrocarbon radical with from 1 to about 8 carbon atoms, and A is an anion, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens such as iodide, chloride and bromide, reference the Abstract of the Disclosure and column 3; a similar teaching is presented in U.S. Pat. No. 4,312,933 which is a division of U.S. Pat. No. 4,291,111; and similar teachings are presented in U.S. Pat. No. 4,291,112 wherein A is an anion including, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens. There are also described in U.S. Pat. No. 2,986,521 reversal developer compositions comprised of toner resin particles coated with finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica.
Also, there are disclosed in U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition. Further, there are disclosed in U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other documents disclosing positively charged toner compositions with charge control additives include U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014; 4,394,430 and 4,560,635 which illustrate a toner with a disteary dimethyl ammonium methyl sulfate charge additive. One disadvantage that may be associated with the charge additive of the '635 patent resides in its apparent inherent instability in some instances as the additive may thermally and chemically degrade, and react with other toner components.
The following prior art, all United States patents, were listed in a patentability search report letter: U.S. Pat. No. 4,812,381 which discloses toners and developers containing charge control agents comprising quaternary ammonium salts of the formula indicated, for example, in the Abstract of the Disclosure, wherein R is alkyl with from 12 to 18 carbon atoms, and the anion is a trifluoromethyl sulfonate; also note, for example, the information presented in columns 2 and 3 of this patent; a similar teaching is presented in U.S. Pat. No. 4,834,921; U.S. Pat. No. 4,490,455 which discloses toners with, for example, amine salt charge enhancing additives, reference the Abstract of the Disclosure for example, and wherein A is an anion including those derived from aromatic substituted sulfonic acids, such as benzene sulfonic acid, and the like, see column 3, beginning at line 33; U.S. Pat. No. 4,221,856 directed to toners with a quaternary ammonium compound wherein A is an anion such as sulfate, sulfonate, nitrate, borate, chlorate, and certain halogens, see the Abstract of the Disclosure; U.S. Pat. No. Re. 32,883 (a reissue of U.S. Pat. No. Re. 4,338,390) illustrates toners with sulfate and sulfonate charge additives, see the Abstract of the Disclosure, wherein R.sub.4 is an alkylene, and the anion contains a R.sub.5 which is a tolyl group, or an alkyl group of from 1 to 3 carbon atoms, and n is the number 3; U.S. Pat. No. 4,323,634 which discloses toners with charge additives of the formulas presented in colum 3, wherein at least one of the R's is a long chain amido group, and X is a halide ion or an organosulfur containing group; U.S. Pat. No. 4,326,019 relating to toners with long chain hydrazinium compounds, wherein the anion A can be a sulfate, sulfonate, phosphate, halides, nitrate, see the Abstract of the Disclosure for example; U.S. Pat. No. 4,752,550 which illustrates toners with inner salt charge additives or mixtures of charge additives, see for example column 8; U.S. Pat. No. 4,684,596 which discloses toners with charge additives of the formula provided in column 3 wherein X can be a variety of anions such as trifluoromethane sulfonate, and U.S. Pat. Nos. 4,604,338; 4,792,513; 3,893,935; 4,826,749, and 4,604,338, the disclosure of each of the aforementioned patents being totally incorporated herein by reference.
The following prior art, all U.S. patents, is mentioned: U.S. Pat. No. 4,812,381 relating to toners and developers with quaternary ammonium salts of the formula illustrated in column 3, the preparation thereof, see column 4, and also note the working Examples, columns 7 and 8, wherein specific charge additives, such as octadecyl ammonium trifluoromethane sulfonate, are reported; U.S. Pat. No. 4,675,118 which discloses certain quaternary salts as fabric softeners, see the Abstract of the Disclosure, and note column 1, for example, wherein X is as recited including OSO.sub.3 CH.sub.3 and halide; U.S. Pat. No. 4,752,550, the disclosure of which is totally incorporated herein by reference, directed to toners and developers with inner salt charge additives and mixtures of such salts with other charge additives, see for example column 4; Reissue 32,883 (a reissue of U.S. Pat. No. 4,338,390), the disclosures of which are totally incorporated herein by reference, wherein toners with organic sulfonate and organic sulfate charge enhancing additives are illustrated, see columns 3, 4, and 5 to 10 for example; and U.S. Pat. No. 4,058,585 which discloses a process of extracting metals with organic solvent solutions of the salts of hydrogen ionic exchange agents, and quaternary ammonium compounds. Processes for preparing quaternary ammonium salts by an ion exchange or ion pair extraction method with soluble quaternary compounds is known, reference for example Phase Transfer Catalysis, Principles and Techniques, Academic Press, N.Y., 1978, especially page 76, C.M. Starks, and C. Liotta, the disclosure of this textbook being totally incorporated herein by reference, and "Preparative Ion Pair Extraction", Apotekarsocieteten/Hassle, Lakemidel, pages 139 to 148, Sweden, 1974, the disclosure of which is totally incorporated herein by reference, which illustrates the preparation of certain bisulfates with water soluble ammonium salt reactants and a two-phase method wherein the product resides in the water phase.
Moreover, toner compositions with negative charge enhancing additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives.
There is illustrated in U.S. Pat. Nos. 4,404,271 a complex system for developing electrostatic images with a toner which contains a metal complex represented by the formula in column 2, for example, and wherein ME can be chromium, cobalt or iron. Additionally, other patents disclosing various metal containing azo dyestuff structures wherein the metal is chromium or cobalt include U.S. Pat. Nos. 2,891,939; 2,871,233; 2,891,938; 2,933,489; 4,053,462 and 4,314,937. Also, in U.S. Pat. No. 4,433,040, the disclosure of which is totally incorporated herein by reference, there are illustrated toner compositions with chromium and cobalt complexes of azo dyes as negative charge enhancing additives.
Illustrated in U.S. Pat. No. 4,937,157, the disclosure of which is totally incorporated herein by reference, are toner compositions comprised of resin, pigment or dye, and tetraalkyl, wherein alkyl, for example, contains from 1 to about 30 carbon atoms, ammonium bisulfate charge enhancing additives such as distearyl dimethyl ammonium bisulfate, tetramethyl ammonium bisulfate, tetraethyl ammonium bisulfate, tetrabutyl ammonium bisulfate, and preferably dimethyl dialkyl ammonium bisulfate compounds where the dialkyl radicals contain from about 10 to about 30 carbon atoms, and more preferably dialkyl radicals with from about 14 to about 22 carbon atoms, and the like. The aforementioned charge additives can be incorporated into the toner or may be present on the toner surface. Advantages of rapid admix, appropriate triboelectric characteristics, and the like are achieved with many of the toners of the aforementioned '157 patent. Advantages of the charge additives of the present invention in embodiments thereof over the additives of the aforementioned '157 patent include improved stable toner admix rate performance; with the quaternary ammonium hydrogen bisulfate salts economical methods for the preparation thereof and purification thereof by a single process step; with the tetraalkyl ammonim alkyl or perfluoroalkyl sulfonates usually more acceptable thermal stability and excellent chemical stability with respect to solvolysis permitting improved shelf stability of, for example, the toner charge enhancing properties, and the like.
Quaternary ammonium bisulfates disclosed in the aforementioned '157 patent can be of the formula R'.sub.2 R".sub.2 N.sup.+ X.sup.-, wherein R' is aryl, substituted aryl such as alkylaryl, alkyl, preferably with 1 to about 30 carbon atoms, such as methyl, ethyl, propyl, butyl, hexyl, heptyl, and preferably dimethyl dialkyl ammonium bisulfate compounds where the dialkyl radicals are from about 10 to about 30 carbon atoms, and more preferably dialkyl radicals with from about 14 to about 22 carbon atoms; R" is aryl, substituted aryl such as alkylaryl, alkyl, preferably containing from 1 to about 18 carbon atoms; and X- is a bisulfate (HSO.sub.4) anion. These charge control additives may be prepared by ionic exchange reactions from a variety of tetrasubstituted ammonium salts, especially those of the formula R'.sub.2 R".sub.2 N.sup.+ X- where X- is selected from the group consisting of halide, alkyl or aryl sulfate, alkoxide, hydroxide, acetate, benzoate and phosphate; and R' and R" are as defined herein. The tetrasubstituted ammonium salt selected can be heated in an appropriate solvent or solvents, such as water, in the presence of a stoichiometric amount of sulfuric acid. One typical process of preparation involves heating at an effective temperature of, for example, from about 40.degree. to about 100.degree. C. for an appropriate period of time, such as from about 5 to about 15 hours, the insoluble tetrasubstituted ammonium chloride or other halide, such as distearyl dimethyl ammonium choride (DDACI), or the corresponding methyl sulfate salt, distearyl dimethyl ammonium methyl sulfate (DDAMS) in aqueous solution, about one molar equivalent in 85 molar equivalents of water and 10 molar equivalents of sulfuric acid in 56 molar equivalents of water. The crude product resulting after cooling to room temperature can be collected by filtration, and then purified by washing with various solvents such as acetone, followed by recrystallization from, for example, an appropriate solvent such as acetone or methanol, and the like. The resulting products can be identified by a number of techniques including melting point information, differential scanning calorimetry, infrared spectra, carbon, and proton nuclear magnetic resonance, ion chromotography, elemental analysis, and the like.
Processes for the preparation of quaternary ammonium bisulfate charge enhancing additives are illustrated in copending application U.S. Ser. No. 396,497 entitled "Quaternary Ammonium Compounds and Processes Thereof", with the listed inventor John L. Haack, the disclosure of which is totally incorporated herein by reference. Also, toner compositions comprised of a mixture of charge enhancing additives wherein one of the additives can be the above bisulfate and processes thereof are illustrated in U.S. Pat. No. 4,904,762, the disclosure of which is totally incorporated herein by reference.
Process embodiments illustrated in the aforementioned copending application and U.S. patent for the preparation of the bisulfate charge additives include the reaction of water insoluble quaternary ammonium salts, such as distearyl dimethyl ammonium methyl sulfate; distearyl dialkyl ammonium halides, such as distearyl dimethyl ammonium halide, especially the chloride or bromide; dialkyl distearyl ammonium hydroxides, wherein alkyl contains from 10 to about 30 carbon atoms, such as dimethyl distearyl ammonium hydroxide, and diethyl distearyl ammonium hydroxide; distearyl ammonium tosylate, such as dimethyl distearyl ammonium tosylate; distearyl dialkyl, wherein alkyl, for example, contains from 1 to about 30 carbon atoms; ammonium alkyl, wherein alkyl, for example, contains from 1 to about 20 carbon atoms; sulfonate; and the like with a sulfuric acid in the presence of heat. Usually a solvent for the acid, such as water, is selected. The acid is selected in effective amounts of, for example, from about 1 to about 10 molar equivalents, and preferably from about 5 to about 8 molar equivalents to about 1 molar equivalent of the quaternary ammonium salt reactant. Heating of the reaction mixture can be accomplished at various temperatures depending, for example, on the reactants selected, preferably the reaction, however, is accomplished at a temperature of from about 40.degree. to about 100.degree. C. Distearyl dimethyl ammonium methyl sulfate can be heated in an appropriate solvent or solvent mixture in the presence of stoichiometric amount of sulfuric acid. The solvent system comprised, for example, of water, water and alcohol mixtures, water and tetrahydrofuran mixtures, water and acetone mixtures, and water and halogenated, especially chlorinated, solvent mixtures may be selected permitting a single phase or two phase system to facilitate the speed thereof by, for example, from days to hours of the reaction and enabling the isolation and purification of the desired quaternary ammonium product. In the one phase method, for example, there is dissolved the DDAMS quaternary ammonium salt reactant and the concentrated sulfuric acid, water, a water miscible organic cosolvent including acetone, dioxane, glycol ethers, tetrahydrofuran, or an aqueous alcohol, preferably methanol or tetrahydrofuran. Thereafter, the resulting solution can be heated, followed by cooling whereby a precipitate of the desired bisulfate product is obtained subsequent to isolation by filtration. The product may be purified by, for example, known recrystallization methods. With a two-phase process, the appropriate quaternary ammonium salt in a solvent such as methylene chloride or chloroform is mixed and heated with an aqueous sulfuric acid solution. One preferred two-phase method comprises heating the appropriate powdered DDAMS quaternary ammonium salt reactant in suspension with excess aqueous sulfuric acid. In the aforementioned two-phase methods, the desired bisulfate product can be isolated directly by filtration, and thereafter purified by recrystallization, or other similar methods when desirable. The resulting products obtained with the process of the present invention can be identified by a number of techniques including melting point information, differential scanning calorimetry, infrared spectra, carbon, and proton nuclear magnetic resonance, ion chromotography, elemental analysis, and the like.
Although many charge enhancing additives are known, there continues to be a need for toners with additives, which toners possess many of the advantages illustrated herein. Additionally, there is a need for positive charge enhancing additives which are useful for incorporation into black and/or colored toner compositions. Moreover, there is a need for colored toner compositions containing certain charge enhancing additives. There is also a need for toner compositions with certain charge enhancing additives, which toners in embodiments thereof possess acceptable substantially stable triboelectric charging characteristics, and excellent admixing properties. Moreover, there continues to be a need for positively charged toner and developer compositions. Further, there is a need for toners with certain charge enhancing additives which can be easily and permanently dispersed into toner resin particles. There also is a need for positively charged black, and colored toner compositions that are useful for incorporation into various imaging processes, inclusive of color xerography, as illustrated in U.S. Pat. No. 4,078,929, the disclosure of which is totally incorporated herein by reference; laser printers; and additionally a need for toner compositions useful in imaging apparatuses having incorporated therein layered photoresponsive imaging members, such as the members illustrated in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Also, there is a need for toner compositions which have the desired triboelectric charge level, for example, from about 10 to about 40 microcoulombs per gram, and preferably from about 10 to about 25 microcoulombs per gram, and admix charging rates of from about 5 to about 60 seconds, and preferably from about 15 to about 30 seconds, as determined by the charge spectrograph, preferably for example at low concentrations, that is for example less than 1 percent, and preferably less than about 0.5 percent of the charge enhancing additive of the present invention.